Various sensors are known in the magnetic-effect sensing arts. Examples of common magnetic-effect sensors include Hall-effect and magnetoresistive technologies. Such magnetic sensors can generally respond to a change in the magnetic field as influenced by the presence or absence of a ferromagnetic target object of a designed shape passing by the sensory field of the magnetic-effect sensor. The sensor can then provide an electrical output, which can be further modified as necessary by subsequent electronics to yield sensing and control information. The subsequent electronics may be located either onboard or outboard of the sensor package.
Hall-effect sensing devices represent one type of magnetic-effect sensors that are utilized widely in rotational and angular position detection. Hall-effect sensors incorporate Hall-effect elements that rely on a reaction between a current flowing between a first set of contacts and an orthogonally-applied magnetic field to generate a voltage across a second set of contacts. In theory, with no magnetic field applied to the Hall-effect element, no voltage should be generated across the second set of contacts. In practice, a voltage is typically generated across the second set of contacts even with no magnetic field applied to the Hall-effect element.
Magnetoresistive (MR) technology is also utilized in a variety of commercial, consumer and industrial detection applications. One type of MR technology is anisotropic magnetoresistive (AMR) technology. In some conventional MR systems an apparatus can be provided for determining the position of a member movable along a path. In such a device, a magnet can be attached to the movable member and an array of magnetic field transducers are located adjacent the path. This type of sensing configuration is commonly referred to as “MR Array” technology. As the magnet approaches, passes and moves away from a transducer, the transducer provides a varying output signal, which can be represented by a single characteristic curve that is representative of any of the transducers.
To determine the position of the movable member, the transducers are electronically scanned and data is selected from a group of transducers having an output that indicates relative proximity to the magnet. A curve-fitting algorithm can then be utilized to determine a best fit of the data to the characteristic curve. By placement of the characteristic curve along a position axis, the position of the magnet and therefore the movable member may be determined.
In another conventional MR device, a position determining apparatus can be implemented, which includes a magnet that is attached to a movable member that moves along a predefined path of finite length. An array of magnetic field transducers can be located adjacent to the predefined path. The transducers can provide an output signal as the magnet approaches passes and moves away from each transducer. A correction mechanism can also be implemented to correct for residual error caused by the non-linearity of the transducers.
Such a correction mechanism preferably approximates the residual error with a predetermined function, and applies correction factors that correspond to the predetermined function to offset the residual error. By correcting for the non-linearity of the transducers, the length of the magnet may be reduced and/or the spacing of the transducers may be reduced.
An example of a conventional magnetic sensing approach is disclosed, for example, in U.S. Pat. No. 5,589,769, “Position Detection Apparatus Including a Circuit for Receiving a Plurality of Output Signal Values and Fitting the Output Signal Values to a Curve,” which issued to Donald R. Krahn on Dec. 31, 1996, and is assigned to Honeywell International Inc. Another example of another conventional magnetic sensing approach is disclosed in U.S. Pat. No. 6,097,183, “Position Detection Apparatus with Correction for Non-Linear Sensor Regions,” which issued to Goetz et al. on Aug. 1, 2000 and is also assigned to Honeywell International Inc. A further example of a conventional magnetic sensing system is disclosed in U.S. Pat. No. 6,806,702, “Magnetic Angular Position Sensor Apparatus,” which issued to Wayne A. Lamb et al on Oct. 19, 2004, and which is assigned to Honeywell International Inc. U.S. Pat. Nos. 5,589,769, 6,097,183 and 6,806,702 are incorporated herein by reference. Such conventional MR-based devices generally utilize discrete components on a Printed Circuit Board (PCB) assembly to yield the resulting function.
Because such conventional MR-based sensing devices, and in particular angle sensors, are required to be implemented in the context of small package diameters, such devices are not feasible in situations where there is not enough room for a bias magnet to be positioned in a “fly by mode”. A magnetic circuit and sensor combination must therefore be implemented, which occupies less space.
Some systems utilize AMR bridges in association with simple mathematical functions such as ATAN (Inverse Tangent function) to determine absolute position data. One of the problems with utilizing mathematical functions such as ATAN is that in order to achieve high accuracy with this method, the AMR bridge signals must be as close to perfect sinusoids (i.e., Sin 2× and Cos 2×) as possible. To date, such goals have not been sufficiently achieved.
In order to overcome such problems, a new angular/rotary position sensing scheme and algorithm thereof must be designed in order to achieve maximum performance benefits. It is believed that the embodiments disclosed herein address and satisfy these issues.